Prior art fisheye lenses such as the DF1.8HB marketed by Fujinon in Japan use a large number of lens elements to obtain the performance requirements of a wide field of view, a large aperture and high image quality. However, the lens assembly is large, heavy and expensive to produce because of the large number of elements used. Additional examples of prior art fisheye lens designs are taught in U.S. Pat. Nos. 3,589,798; 3,597,049; 3,734,600; 3,737,214; 3,741,630; 4,412,726; 6,844,991; 7,173,776; 7,161,746; publication US 2005/0219715 A1 and also in JP Patents 63-017421, and 60-153018. The number of lens elements in the lenses taught by these references range from 8 to 15 elements whereas the invention taught by this application achieves similar results with only six lens elements thereby reducing complexity and cost.
In U.S. Pat. No. 7,023,628 issued on Apr. 4, 2006, this same or common inventor disclosed a compact fisheye lens with only six elements. In Japanese publications 04267212, 04068307 and 2002072085, various combinations of six element lenses were also disclosed. However, there is a need to further improve the optical performance of those lenses and/or reduce the manufacturing cost of them by offering less complex and an improved design such as that taught herein and below.